Method and apparatus for casting aluminum by casting mold

Abstract

An aluminum casting process using a casting mold in which after the cavity ( 25 ) is filled with an inert gas, magnesium is introduced in to the cavity to have a magnesium layer ( 58 a ) deposited on the cavity wall. Then, nitrogen gas is introduced into the cavity to form magnesium nitride ( 58 b ) on the surface of the magnesium layer after the cavity wall is heated to a specific temperature. Then, molten aluminum is supplied to have an aluminum casting molded, while the surface of the molten aluminum ( 39 ) is reduced with magnesium nitride. This makes it possible to form magnesium nitride within a short time and decrease the amount of nitrogen gas as required.

1. An aluminum casting process using a casting mold, comprising the steps of:
 filling a cavity of a closed mold with an inert gas; 
 introducing gaseous magnesium into the inert gas-filled cavity and thereby depositing magnesium on a wall of the cavity; 
 heating the mold to heat only an area of the magnesium-deposited cavity wall corresponding to a casting portion of small thickness to a specific temperature; 
 after heating the mold, introducing nitrogen gas into the cavity and thereby forming magnesium nitride on the cavity wall; and 
 supplying molten aluminum into the cavity in which the magnesium nitride has been formed, to mold an aluminum casting in the cavity, while reducing a surface of the molten aluminum with the magnesium nitride. 
 
     
     
       2. The aluminum casting process using a casting mold according to  claim 1 , comprising the further step of detecting a temperature of the cavity wall with a thermocouple embedded in the mold. 
     
     
       3. The aluminum casting process using a casting mold according to  claim 2 , wherein the thermocouple is installed in a cavity wall area corresponding to the casting portion of small thickness to detect a temperature of said cavity wall area. 
     
     
       4. An aluminum casting process using a casting mold, comprising the steps of:
 filling a cavity of a closed mold with an inert gas; 
 introducing gaseous magnesium into the inert gas-filled cavity and thereby depositing magnesium on a wall of the cavity; 
 heating the mold to heat the magnesium-deposited cavity wall to a specific temperature; 
 detecting a temperature of the cavity wall with a thermocouple embedded in the mold in a cavity wall area corresponding to a casting portion of small thickness to detect a temperature of said cavity wall area; 
 after heating the mold, introducing nitrogen gas into the cavity and thereby forming magnesium nitride on the cavity wall; and 
 supplying molten aluminum into the cavity in which the magnesium nitride has been formed, to mold an aluminum casting in the cavity, while reducing a surface of the molten aluminum with the magnesium nitride. 
 
     
     
       5. An aluminum casting process using a casting mold, comprising the steps of:
 filling a cavity of a closed mold with an inert gas; 
 introducing gaseous magnesium into the inert gas-filled cavity and thereby depositing magnesium on a wall of the cavity; 
 introducing heated nitrogen gas into the cavity so as to form magnesium nitride on the cavity wall while selecting a temperature T (° C.) of gas in the cavity and a pressure P (atmosphere) in the cavity so as to maintain a relationship T≧(130×P+270); and 
 supplying molten aluminum into the cavity in which the magnesium nitride has been formed, to mold an aluminum casting in the cavity, while reducing a surface of the molten aluminum with the magnesium nitride. 
 
     
     
       6. An aluminum casting process using a casting mold, comprising the steps of:
 filling a cavity of a closed mold with an inert gas, while discharging air from the cavity, to establish a first pressure in the cavity; 
 introducing gaseous magnesium into the cavity to deposit magnesium on a wall of the cavity and establish a second pressure in the cavity; 
 introducing heated nitrogen gas into the cavity to form magnesium nitride on the wall of the cavity and establish a third pressure in the cavity; 
 selecting the third pressure P and the temperature T of gas in the cavity so as to maintain a relationship P*(T−270)/130; and 
 supplying molten aluminum into the cavity to mold an aluminum casting in the cavity, while reducing a surface of the molten aluminum with the magnesium nitride. 
 
     
     
       7. An aluminum casting process using a casting mold, comprising the steps of:
 filling a cavity of a closed mold with an inert gas, while discharging air from the cavity, to establish a first pressure in the cavity that is equal to an atmospheric pressure; 
 introducing gaseous magnesium into the cavity to deposit magnesium on a wall of the cavity and establish a second pressure in the cavity that is equal to the atmospheric pressure; 
 introducing heated nitrogen gas into the cavity to form magnesium nitride on the wall of the cavity and establish a third pressure in the cavity that is a negative pressure below the atmospheric pressure; and 
 supplying molten aluminum into the cavity to mold an aluminum casting in the cavity, while reducing a surface of the molten aluminum with the magnesium nitride. 
 
     
     
       8. An aluminum casting process using a casting mold, comprising the steps of:
 filling a cavity of a closed mold with an inert gas; 
 introducing gaseous magnesium into the inert gas-filled cavity and thereby depositing magnesium on a wall of the cavity; 
 heating the cavity wall of the mold, with a cartridge heater embedded in the mold, to heat only an area of the magnesium-deposited cavity wall corresponding to a casting portion of small thickness to a specific temperature; 
 after heating the mold, introducing nitrogen gas into the cavity and thereby forming magnesium nitride on the cavity wall; and 
 supplying molten aluminum into the cavity in which the magnesium nitride has been formed, to mold an aluminum casting in the cavity, while reducing a surface of the molten aluminum with the magnesium nitride. 
 
     
     
       9. An aluminum casting process using a casting mold, comprising the steps of:
 filling a cavity of a closed mold with an inert gas; 
 introducing gaseous magnesium into the inert gas-filled cavity and thereby depositing magnesium on a wall of the cavity; 
 heating the mold with a cartridge heater embedded in the mold, to heat the magnesium-deposited cavity to a specific temperature; 
 heating the mold to heat the magnesium-deposited cavity wall to a specific temperature; 
 detecting a temperature of the cavity wall with a thermocouple embedded in the mold in a cavity wall area corresponding to a casting portion of small thickness to detect a temperature of said cavity wall area; 
 after heating the mold, introducing nitrogen gas into the cavity and thereby forming magnesium nitride on the cavity wall; and 
 supplying molten aluminum into the cavity in which the magnesium nitride has been formed, to mold an aluminum casting in the cavity, while reducing a surface of the molten aluminum with the magnesium nitride.